The American Navy experiment measured the ocean with
A、heat
B、light
C、rope
D、sound
Task 220. It is popularly believed that all research needs ca21. One should make sure the research is____22. It is as difficult to solve a useful problem as to23. One may need some simple equipment to overcome24. Not many people realize that it is difficult to25. Failures in research A. happen very oftenB. worth doingC. do somethingnewD. lose one's patienceE. solve a useless oneF. expensive scientific equipmentG. the major difficulties in research
German workers feel Germany is the proper place for foreigners.